Landing approach method with distributed propulsion units

Abstract

An aircraft (1) has a wing (2) with two half-wings (3, 4), at least three propeller drives (5) arranged side by side on a leading edge of each half-wing (3, 4), the propellers (18) of which rotate about propeller axes (17) and whose propeller wakes blow on the respective half-wing (3, 4), and a landing flap (7, 8) arranged on a trailing edge (6) of each half-wing (3, 4). When the aircraft (1) lands, the landing flaps (7, 8) are extended, and at least one of the propeller drives (5), which is arranged on the respective half-wing (3, 4) in front of the extended landing flap (7, 8), generates a primary propeller thrust in the forward direction of its propeller axis (17) that is at least 15% greater than that generated on the respective half-wing (3, 4) not in front of the extended landing flap (7, 8).

Description

TECHNICAL FIELD OF THE INVENTION

[0001] The invention relates to a method for flying an aircraft with a wing comprising two half-wings and at least three propeller drives arranged side by side on a leading edge of each of the half-wings. The propellers rotate around propeller axes and the propeller wakes blow air onto the respective half-wing. In particular, the invention relates to a method having the features of the preamble of independent patent claim 1. Furthermore, the invention relates to a corresponding aircraft with a control system for implementing the method. STATE OF THE ART

[0002] The electrification of aircraft propulsion opens up new possibilities for the distribution and placement of propulsion units. This includes the distribution of multiple propeller drives along the leading edges of the wing, which provides a larger portion of the wing with propeller wakes. Distributed propulsion of this type significantly increases wing lift during low-speed flight. This effect is beneficial during takeoff, when high thrust is required. During landing, when the required thrust is typically lower, the potential for lift decreases with the thrust requirement.

[0003] To achieve a particularly large increase in lift by blowing air onto the half-wings, NASA has developed the concept of so-called "high-lift propellers," see Nicholas K. Borer et al.: Design and Performance of the NASA SCEPTOR Distributed Electric Propulsion Flight Demonstrator, American Institute of Aeronautics and Astronautics (AIAA), 2019, https: / / ntrs.nasa.gov / search.jsp?R=20160010157. According to this concept, conventional propellers are installed at the wingtips and serve exclusively to generate thrust.

[0004] Additionally, high-lift propellers are installed along the leading edges of the wings, primarily used to increase lift during slow flight. The propeller blades of the high-lift propellers are designed to significantly increase the lift of the downstream half-wing, but generate relatively little thrust. During cruise flight, the propeller blades of the high-lift propellers are folded in, driving only the conventional propellers. During landing, the conventional propellers can be used in so-called "windmilling" mode to increase drag, allowing the high-lift propellers to generate more lift with the same effective total thrust.

[0005] US Pat. No. 9,751,614 B1 discloses a method for modifying the flight dynamics of an aircraft during flight. The aircraft has a distributed propulsion system with several jet engines arranged below the two half-wings of its wing. By operating the jet engines at different thrust levels, the half-wings are deliberately twisted around their spanwise direction. In particular, the jet engines located further outwards generate more thrust than the jet engines located further inwards.

[0006] DE 11 2020 004 729 T5 discloses an electric aircraft and a method for controlling its aerodynamic performance. The electric aircraft has several propeller drives arranged along the leading edges of its half-wings, which contribute to the lift of the half-wings. The primary propeller thrusts of the individual propeller drives are adjusted depending on an aerodynamic force generated on the wing such that an effective total thrust or the aerodynamic force acting on the entire electric aircraft has a predetermined value or lies within a predetermined range. The primary propeller thrust generated by individual propeller drives can also be set to a negative value. By adjusting the primary propeller thrust of the individual propeller drives, a desired lift distribution is achieved.The lift can be distributed over the half-wings in such a way that it decreases towards the wing tips, thus reducing the bending moment acting on the half-wings.

[0007] DE 202016 000269 U1 discloses an aircraft with a wing on each side, which has at least one intake opening along its leading edge and at least one exhaust opening along its trailing edge. Inside the wing are fan units arranged side by side, each associated with an intake opening and an exhaust opening.

[0008] WO 2023 / 034302 A1 discloses a system and method for increasing the lift of an aircraft wing having a leading edge and a trailing edge. A plurality of thrust-generating devices are connected to the aircraft wing. They include a flap connected to an inner portion of the aircraft wing near the trailing edge, and an aircraft roll control device connected to the aircraft wing. The thrust-generating devices each have a wake and a flap that can be adapted to bend away from an edge of the aircraft wing.

[0009] EP 3 093 235 A1 discloses an aircraft having trailing edge flaps and a wing-mounted propulsion element. The propulsion element is arranged such that the flaps on the wing are in a wake of the propulsion element when extended. The aircraft further comprises a thrust-vectored propulsion element configured to selectively vary the exhaust exhaust vector of the propulsion element in at least one plane. The thrust-vectored propulsion includes an engine convertible between two modes: a first mode in which the engine provides net forward thrust to the aircraft and a second mode in which the engine provides net drag to the aircraft. The engine is positioned to induct a boundary layer airflow when operating in the first mode.

[0010] US 2020 / 0 407 060 A1 discloses aircraft designs, in particular with tandem wings and a distributed propulsion system. In one embodiment, the tandem wings comprise a first and a second set of wings, each having a wingspan with a row of thrusters. OBJECT OF THE INVENTION

[0011] The invention is based on the object of demonstrating a simple to implement but effective method for flying an aircraft with several propeller drives arranged next to one another on a wing leading edge of each of its half-wings, whose propellers rotate around propeller axes and whose propeller wakes blow onto the half-wing, which method ensures sufficient lift even when the aircraft lands at very low flight speed. SOLUTION

[0012] The object of the invention is achieved by a method having the features of independent patent claim 1 and by an aircraft having the features of independent patent claim 9. The dependent patent claims are directed to preferred embodiments of the method according to the invention and the aircraft according to the invention. DESCRIPTION OF THE INVENTION

[0013] In a method according to the invention for flying an aircraft with a wing comprising two half-wings, at least three propeller drives arranged side by side on a leading edge of each of the half-wings, the propellers of which rotate about propeller axes aligned at least substantially parallel to one another and whose propeller wakes blow against the respective half-wing, and at least one landing flap arranged on a trailing edge of each of the half-wings, the landing flaps are extended when the aircraft lands, and at least one of the propeller drives arranged on the respective half-wing in front of the extended landing flap generates a primary propeller thrust in the forward direction of its propeller axis that is at least 15%, preferably at least 25% and most preferably at least 35% greater than at least one of the propeller drives,which is not located in front of the extended landing flap on the respective half-wing.

[0014] The method according to the invention is based on the idea of ​​equipping the aircraft exclusively with identical propeller drives, whereby the directions of rotation of all propellers, or at least of all propellers on each half-wing, around their propeller axes can be the same, but do not have to be the same. A mirror-image distribution of the directions of rotation of the propellers on the two half-wings is also possible, but not mandatory. In order to decouple the increase in lift caused by the propeller wakes when the aircraft lands from the overall thrust acting on the aircraft, propeller drives arranged in front of the extended landing flaps during landing generate significantly greater primary propeller thrusts in the forward direction of their propeller axes than propeller drives not arranged in front of the extended landing flaps.The primary propeller thrust of the respective propeller drive in the forward direction of its propeller axis is the thrust with which the propeller of the respective propeller drive pulls the half-wing forward in the direction of the propeller axis. Relative to their primary propeller thrusts, the propeller drives arranged in front of the extended landing flaps achieve a greater increase in lift and a smaller increase in the effective total thrust acting on the entire aircraft along the propeller axes in the forward direction than the propeller drives not arranged in front of the extended landing flaps. The effective total thrust considered here is the sum of all primary propeller thrusts, drags, including the drag induced by the propeller wakes, and other forces acting on the aircraft along the propeller axes.The comparatively large increase in lift with a comparatively small increase in total thrust in the forward direction occurs particularly when the propeller drives, which are not located in front of the extended landing flaps, are positioned further out on the wing hemispheres. If the small effective total thrust required during the landing approach is generated primarily by the propeller drives in front of the extended landing flaps, a much greater increase in lift can be achieved than if the same effective total thrust were generated with the propeller drives not located in front of the extended landing flaps. The potential for increasing lift with a small increase in effective total thrust is greatest in front of the extended landing flaps in the inner region of the wing.This can be exploited in the method according to the invention by generating, during landing, a primary propeller thrust in the forward direction of its propeller axis that is preferably at least 10% greater with one of the propeller drives arranged further inward on the respective half-wing in front of the extended landing flap than with one of the propeller drives arranged further outward on the respective half-wing in front of the extended landing flap. During takeoff or during cruise of the aircraft, the distribution of the primary propeller thrusts of the propeller drives in the forward directions of their propeller axes can be modified such that the required lift is generated together with a higher effective total thrust for the aircraft.For this purpose, the propeller drives positioned in front of the extended flaps can generate less primary propeller thrust, and the propeller drives not positioned in front of the extended flaps can generate more primary propeller thrust than during landing. The ratio of the increased lift from the propeller wakes to the effective total thrust of all propeller drives acting on the aircraft as a whole can be continuously varied.

[0015] The relationship between the primary propeller thrust of one of the propeller drives in the forward direction of its propeller axis to the effective total thrust acting on the aircraft on the one hand and the increase in lift caused by the propeller wake on the other hand is influenced not only by the position of the propeller drive in front of or next to the extended landing flaps and the position of the propeller drive in the inner or outer area of ​​the wing, but also significantly by whether the propeller drive is arranged in front of a deflected aileron on the trailing edge of the respective wing or also next to such a deflected aileron.For example, two symmetrically arranged ailerons on both half-wings can be deflected downwards in the same direction during landing. With at least one of the propeller drives arranged on the respective half-wing in front of the deflected aileron, a primary propeller thrust in the forward direction of its propeller axis can be generated that is preferably at least 10% greater than with at least one of the propeller drives arranged on the respective half-wing neither in front of the deflected aileron nor in front of an extended landing flap. This also achieves a greater increase in lift in relation to the contribution to the effective total thrust. However, the effect is not as great as with a propeller drive in front of an extended landing flap on the inner region of the wing.

[0016] It is of fundamental advantage if, during landing, all propeller drives arranged in front of the extended landing flaps or deflected ailerons generate primary propeller thrusts in the forward direction of their propeller axes that are preferably at least 15% greater than those generated by all propeller drives not arranged in front of the extended landing flaps or deflected ailerons.

[0017] In principle, the ailerons can also be deflected upwards in the same direction using the method according to the invention. The propeller drives arranged in front of them can be controlled to generate primary propeller thrusts in the forward direction, but also to generate negative propeller thrusts, i.e., propeller thrusts in the reverse direction of their propeller axes. This allows, for example, the generation of lift to be concentrated on the inner regions of the half-wings, thus reducing the effective wingspan of the aircraft.

[0018] The primary propeller thrust in the forward direction of the propeller axis can be varied by changing the speed of the respective propeller drive and / or changing the propeller blade pitch of the respective propeller drive. The relationship between the drive power with which the propeller drive is operated and the resulting primary propeller thrust is non-linear. Thus, with propeller drives that generate less primary propeller thrust, the spin of the propeller wakes can be varied in such a way that the aircraft's induced drag is increased. This induced drag can be compensated for in the event of a lift demand by increasing the primary propeller thrusts that result in a particularly large increase in lift.In particular, the propeller drives used to generate greater primary propeller thrusts during landing can be operated with a greater, equal, or lower drive power than / as those of the propeller drives used to generate smaller primary propeller thrusts in the forward directions of their propeller axes. The speeds of the propeller drives used to generate greater primary propeller thrusts during landing can also be greater, equal, or lower than / as the speeds of the propeller drives used to generate smaller primary propeller thrusts in the forward directions of their propeller axes.

[0019] In extreme cases, when landing with at least one of the propeller drives on each half-wing engaged, a particularly small primary propeller thrust is generated in the forward direction of its propeller axes by generating a negative primary propeller thrust in the forward direction of its propeller axes, i.e., a primary propeller thrust in the reverse direction of its propeller axes and thus opposite to the direction of flight. Then, with the propeller drives positioned in front of the extended landing flaps and any ailerons deflected downwards in the same direction, which lead to a significant increase in lift, particularly large primary propeller thrusts can be generated in the forward directions of their propeller axes without the effective total thrust acting on the aircraft as a whole becoming unintentionally large.

[0020] Even though the effective total thrust in the direction of flight can be generated primarily by the propeller drives located further outboard during the aircraft's cruise flight, thrust in the direction of flight is preferably generated by all propeller drives on both half-wings. Particularly preferred is then that all propeller drives generate approximately equal primary propeller thrusts and / or equal contributions to the effective total thrust.

[0021] The wing is preferably aerostructurally designed for cruising flight, as is usual for aircraft. The influence of the propeller drives on lift is taken into account. The method according to the invention is also applicable to different propeller drives, which can be used, for example, to minimize induced and ultimately total drag. This possibility is particularly, but not exclusively, available for propeller drives arranged at the wing tips. Another possible application of the measures of the method according to the invention is the adaptation of the load distribution with changing aircraft mass and unchanged flight altitude and / or flight speed. The individual propeller drives on the half-wings generate different primary propeller thrusts, resulting in an optimal lift distribution for the current flight condition.During the approach, the primary propeller thrusts are changed to optimize lift generation and allow a lower landing speed.

[0022] In an extension of the method according to the invention, the induced drag of the aircraft is deliberately increased in certain flight situations by changing the lift and / or circulation distribution across the half-wings. During the approach to landing, higher drag is desired – the aircraft can thus descend with more effective total thrust. The additional effective total thrust required to overcome the higher drag can then be used to generate additional lift. For this purpose, a deviation from the optimal lift distribution, which would lead to minimal induced drag, is induced. In slow flight at low airspeeds, particularly during the approach to landing, i.e., during landing, the drag consists largely of induced drag. The drag induced by the half-wings depends not only on the strength of the wing circulation but also on the circulation distribution.By measures such as varying flap deflections along the wingspan, the circulation distribution can be varied and thus the induced drag increased. The possibility of using the ailerons to influence the lift distribution has already been mentioned. According to the invention, by specifically varying the primary propeller thrusts generated by the individual propeller drives in the forward directions of their propeller axes, the aerodynamic forces along the half-wings are redistributed compared to their ideal distribution, thereby increasing the induced drag of the half-wings. In principle, lift can also be redistributed by changing the direction of rotation of the propellers of individual propeller drives, and thus the lift distribution can be negatively influenced. In particular, negative primary propeller thrust can be generated by changing the direction of rotation of the propellers of the propeller drives.When using propeller drives with variable-pitch propellers, i.e., propeller blades with adjustable angles of attack, the spin of the propeller wakes can also be decoupled from the primary propeller thrust. This allows for a higher spin with the same primary propeller thrust, which in turn can lead to significant inhomogeneity in the lift distribution and ultimately to increased induced drag.

[0023] Increased induced drag during landing can also be caused by the propeller drives on one half-wing generating different primary propeller thrusts in the forward directions of their propeller axes than the corresponding paired propeller drives on the other half-wing. The resulting asymmetric lift distribution produces the desired increase in induced drag. This can also be combined with different aileron deflections to increase the asymmetry of the lift distribution and consequently the induced drag.

[0024] Influencing the lift distribution across the wings through the different primary propeller thrusts generated by the individual propeller drives also provides advantages in the event of a go-around during a failed landing. Since the induced drag is increased during the approach to landing by specifically adjusting the individual propeller drives, changing these settings to generate maximum thrust leads to a comparatively rapid improvement in the lift distribution with regard to induced drag and thus aerodynamic efficiency.

[0025] The inventive increase in induced drag has another advantage over drag generation using propellers, spread flaps, or airbrakes. Since the increase in induced drag does not require a stall to generate drag, it is potentially significantly quieter. Furthermore, the method is potentially more effective, since induced drag is dominant in slow flight. However, the inventive increase in induced drag does not preclude combination with other drag generation concepts.

[0026] An aircraft according to the invention, comprising a wing with two half-wings, at least three propeller drives arranged side by side on a leading edge of each of the half-wings, whose propeller axes are aligned at least substantially parallel to each other and whose propeller wakes blow the respective half-wing, a landing flap arranged on a trailing edge of each half-wing, and typically also an aileron arranged on the trailing edge of each of the half-wings, has a control system for implementing the method according to the invention. This control system can be part of an autopilot of the aircraft.

[0027] The propeller drives of the aircraft according to the invention can, in particular, be electric drives. All propeller drives on the half-wings can have identical electric motors and identical propeller blades. The propeller blades can be adjustable in their angle of attack; in other words, the propeller drives can have variable-pitch propellers.

[0028] Typically, no propeller drives other than those whose propeller wakes blow the respective half-wing are mounted on the wings of the aircraft according to the invention. Thus, different propellers, such as high-lift propellers on the one hand and high-thrust propellers on the other, are generally provided. Rather, the relationship between the increased lift and the effective total thrust is influenced by different primary propeller thrusts in the direction of flight and, if applicable, by different spins of the propeller drives distributed across the leading edges of the wings.

[0029] In the aircraft according to the invention, at least three, typically at least four, propeller drives are arranged on each of the half-wings, whose propeller wakes blow air onto the respective half-wing. Often, there are five or six such propeller drives. BRIEF DESCRIPTION OF THE CHARACTERS

[0030] In the following, the invention is further explained and described with reference to preferred embodiments shown in the figures. Fig. 1 is a schematic representation of an aircraft according to the invention during landing in a rear view. Fig. 2 shows a lift distribution over the aircraft according to Fig. 1 when landing, when all of its propeller drives generate equal primary propeller thrusts in the forward directions of their propeller axes. Fig. 3 shows a lift distribution over the aircraft according to Fig. 1when landing, when its propeller drives in the inner wing area generate larger primary propeller thrusts in the forward directions of their propeller axes, while its propeller drives at the wing tips even generate negative primary propeller thrusts in the forward directions of their propeller axes, ie primary propeller thrusts in the backward directions of their propeller axes, where the dashed line shows the lift distribution according to Fig. 2 is reproduced. Fig. 4 shows a lift distribution over the aircraft according to Fig. 1 when landing, with the propeller drives in the inner wing area opposite Fig. 3 increased primary propeller thrusts are generated in the forward directions of their propeller axes to compensate for increased induced drag caused by the change in lift distribution according to Fig. 2 (here dashed line) to the buoyancy distribution according to Fig. 3 (here dotted line) is created. Fig. 5 shows a lift distribution over the aircraft according to Fig. 1 when landing with an opposite Fig. 1 varied flap position, whereby again the lift distribution according to Fig. 2 shown with a dashed line for comparison. Fig. 6 shows a lift distribution of the aircraft according to the invention when landing with Fig. 5 in the inner wing area, increased primary propeller thrusts of the propeller drives in the forward directions of their propeller axes to compensate for the drag caused by the increased flap deflection and the change in lift distribution according to Fig. 2 (here dashed line) to the buoyancy distribution according to Fig. 5 (here dotted line) is created. FIGURE DESCRIPTION

[0031] The Fig. 1Aircraft 1, depicted from behind during landing approach, has a fuselage 9, a vertical stabilizer 10, a horizontal stabilizer 11, and a wing 2 with two half-wings 3 and 4. Six propeller drives 5 are evenly distributed along the leading edges of the half-wings 3 and 4 facing away from the viewer. The propeller drives 5 are each distributed from an inner wing region adjoining the fuselage 9 to an outer wing region ending at a wing tip of the wing 3 or 4. Each of the propeller drives 5 has a propeller 18 rotating around a propeller axis 17, in this case with six propeller blades 19. Propeller wakes of the propeller drives 5 blow the respective half-wings 3 and 4 and thus lead to an increase in the lift of the respective half-wings 3 and 4. An inner landing flap 7 and an outer landing flap 8 are arranged on the trailing edges 6 of the half-wings 3 and 4 facing the observer. Fig. 1, which shows aircraft 1 during landing, all flaps 7 and 8 are fully extended.

[0032] Fig. 2 shows a lift distribution 12 across the wingspan of the aircraft 1 during landing, when all propeller drives 5 generate equal primary propeller thrusts in the forward direction of their propeller axes 17, i.e., in the direction of flight. The components of the effective total thrust on the aircraft in the upstream direction, i.e., in the direction of flight, resulting from the primary propeller thrusts, plus the resultant of the gravitational force of the aircraft 1 in the upstream direction, correspond to the aerodynamic drag of the aircraft 1, so that the effective total thrust on the aircraft is zero and an unaccelerated flight condition prevails.

[0033] Fig. 3 shows, in addition to the buoyancy distribution 12 shown here with a dashed line, according to Fig. 2a lift distribution 13 for the case where the primary propeller thrusts generated by the four propeller drives 5, located in the inner wing area in front of the extended landing flaps 7 and 8, are increased in the forward directions of their propeller axes 17, while the propeller drives 5 at the wing tips of half-wings 3 and 4 generate primary propeller thrusts in the reverse directions of their propeller axes 17, i.e., negative primary propeller thrusts in the forward directions of their propeller axes 17. The sum of the primary propeller thrusts in the forward directions of their propeller axes 17 remains unchanged. However, compared to lift distribution 12, an increase in total lift is evident. In addition, higher induced drag is to be expected with lift distribution 13 compared to lift distribution 12.This increased drag can be compensated for by additionally increasing the primary propeller thrust of the propeller drives in the inner wing area. This further increases the local lift in the inner wing area and thus the overall lift, as shown by the corresponding lift distribution 14 shown in . Fig. 4 shows.

[0034] The lift distribution can also be changed by varying the deflection of the landing flaps 7 and 8 across the span. Fig. 5 shows this for a case with opposite Fig. 1 unchanged segmentation of the landing flaps 7 and 8. The inner landing flaps 7 are according to Fig. 5 opposite Fig. 1 slightly retracted, while the outer landing flaps 8 are more extended in comparison. If one takes a lift distribution 12 according to Fig. 2 unchanged total lift of the resulting lift distribution 15 according to Fig. 5, the changed lift distribution 15 still affects the induced drag. The increased induced drag can be compensated by increasing the primary propeller thrusts of the propeller drives 5 in the wing inner regions, resulting in a further increased lift in the wing inner regions, as shown by the resulting lift distribution 16 according to Fig. 6 shows. LIST OF REFERENCE SYMBOLS

[0035] 1Aircraft 2Wing 3Half-wing 4Half-wing 5Propeller drive 6Trailing edge 7Landing flap 8Landing flap 9Fuselage 10Vertical stabilizer 11Elevator 12Lift distribution 13Lift distribution 14Lift distribution 15Lift distribution 16Lift distribution 17Propeller shaft 18Propeller 19Propeller blade

Claims

1. A method for flying an aircraft (1) with a wing (2) comprising two half-wings (3, 4), at least three propeller drives (5) arranged side by side on a leading edge of each of the half-wings (3, 4), the propellers (18) of which rotate around propeller axes (17) and whose propeller wakes blow against the respective half-wing (3, 4), and a landing flap (7, 8) arranged on a trailing edge (6) of each of the half-wings (3, 4), - wherein, in certain flight conditions, the at least three propeller drives (5) on the respective half-wing (3, 4) generate different primary propeller thrusts in the forward directions of their propeller axes (17), and - wherein the landing flaps (7, 8) are extended when the aircraft (1) lands, characterized in thatwhen landing with at least one of the propeller drives (5) arranged on the respective half-wing (3, 4) in front of the extended landing flap (7, 8), a primary propeller thrust in the forward direction of its propeller axis (17) that is at least 15% greater is generated than with at least one of the propeller drives (5) that is not arranged on the respective half-wing (3, 4) in front of the extended landing flap (7, 8).

2. Method according to claim 1, characterized in that when landing with one of the propeller drives (5) which is arranged further inward on the respective half-wing (3, 4) in front of the extended landing flap (7, 8), a primary propeller thrust in the forward direction of its propeller axis (17) which is at least 10% greater is generated than with one of the propeller drives (5) which is arranged further outward on the respective half-wing (3, 4) in front of the extended landing flap (7, 8).

3. Method according to claim 1 or 2, wherein the aircraft (1) has an aileron on each of the two half-wings (3, 4), characterized in that the two ailerons on the two half-wings (3, 4) are deflected in the same direction during landing and that during landing with at least one of the propeller drives (5) which is arranged on the respective half-wing (3, 4) in front of the deflected aileron, a primary propeller thrust in the forward direction of its propeller axis (17) which is at least 10% greater is generated than with at least one of the propeller drives (5) which is arranged on the respective half-wing (3, 4) neither in front of the deflected aileron nor in front of the extended landing flap (7, 8).

4. Method according to one of the preceding claims, characterized in thatwhen landing with all propeller drives (5) arranged in front of the extended landing flaps (7, 8) or deflected ailerons, primary propeller thrusts in the forward directions of their propeller axes (17) are generated that are at least 15% greater than with all propeller drives (5) not arranged in front of the extended landing flaps (7, 8) or the deflected ailerons.

5. Method according to one of the preceding claims, characterized in that when landing, those of the propeller drives (5) with which larger primary propeller thrusts are generated in the forward directions of their propeller axes (17) are operated with greater, equal or smaller drive power than / as those of the propeller drives (5) with which smaller primary propeller thrusts are generated in the forward directions of their propeller axes (17).

6. Method according to one of the preceding claims, characterized in thatwhen landing with at least one of the propeller drives (5) on each half-wing (3, 4) which is not arranged in front of the extended landing flaps (7, 8) on the respective half-wing (3, 4), primary thrust is generated in the rearward direction of its propeller axis (17).

7. Method according to one of the preceding claims, characterized in that when landing with the propeller drives (5) on one half-wing (3), different primary propeller thrusts are generated in the forward directions of their propeller axes (17) than with the propeller drives (5) corresponding to them in pairs on the other half-wing (4) of the two half-wings (3, 4).

8. Method according to one of the preceding claims, characterized in that During cruising flight of the aircraft (1), all propeller drives (5) on the two half-wings (3, 4) generate propeller thrusts in the forward directions of their propeller axes (17).

9. Aircraft (1) with - a wing (2) having two half-wings (3, 4), - at least three propeller drives (5) arranged next to one another on a leading edge of each of the half-wings (3, 4), the propellers (18) of which rotate about propeller axes (17) and the propeller wakes of which blow the respective half-wing (3, 4), - a landing flap (7, 8) arranged on a trailing edge (6) of each half-wing (3, 4) and - a controller for carrying out the method according to one of the preceding claims.

10. Aircraft (1) according to claim 9, characterized in that , an aileron is arranged on the trailing edge (6) of each of the half-wings (3, 4).

11. Aircraft (1) according to claim 9 or 10, characterized in that all propeller drives (5) on the half-wings (3, 4) have identical or mirror-symmetrical electric motors and identical or mirror-symmetrical propeller blades (19).

12. Aircraft (1) according to one of claims 9 to 11, characterized in that the propeller wakes of all propeller drives (5) arranged on the wings (2) blow onto the respective half-wings (3, 4).

13. Aircraft (1) according to one of claims 9 to 12, characterized in that at least 4, preferably at least 5 propeller drives (5) are arranged on each of the half-wings (3, 4), the propeller wakes of which blow the respective half-wing (3, 4).

14. Aircraft (1) according to one of claims 9 to 13, characterized in that at least one propeller drive (5) on each of the half-wings (3, 4) has a controllable propeller with adjustable propeller blades (19).

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